输入捕获测得的频率不正确 是什么原因？

骑猪兜风66888

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);  
GPIO_InitStructure.GPIO_Pin  = GPIO_Pin_8;    
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPD; //PB8 ????????
GPIO_Init(GPIOB, &GPIO_InitStructure); 

GPIO_ResetBits(GPIOB,GPIO_Pin_8);


TIM_TimeBaseStructure.TIM_Period = 0XFFFF; 
  TIM_TimeBaseStructure.TIM_Prescaler =24-1;   
  TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; 
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; 
  TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure); 
  
    
  TIM4_ICInitStructure.TIM_Channel = TIM_Channel_3; 
  TIM4_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;       
  TIM4_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI; 
  TIM4_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;       
  TIM4_ICInitStructure.TIM_ICFilter = 0x00;
  TIM_ICInit(TIM4, &TIM4_ICInitStructure);

void TIM4_IRQHandler(void)
{ 

if (TIM_GetITStatus(TIM4, TIM_IT_CC3) != RESET)
{   
TIM_ClearITPendingBit(TIM4,TIM_IT_CC3); 
 if(CaptureNumber3== 0)
{
IC4ReadValue3=TIM_GetCapture3(TIM4);
CaptureNumber3=1;
}
else if(CaptureNumber3)
{
CaptureNumber3=0;
IC4ReadValue4=TIM_GetCapture3(TIM4);
if(IC4ReadValue4>IC4ReadValue3)
{
Capture=IC4ReadValue4-IC4ReadValue3;
}else
{
Capture3=((0xffff-IC4ReadValue3)+IC4ReadValue4);

}
Freq3=24000000.0/Capture3;

}
}

这是源代码 是什么原因导致的呢？？求指导

正点原子

得慢慢调试。。。
你自己分析下先。